Apparatus for mixing plastics has been shown in such patents as DT-OS 2,007,935. In this known apparatus, the mixing head has a cylindrical bore in which a control member in the form of a piston is mounted for axial displacement. Because a seal ring would be destroyed by the displacement of the control member on the edges of the injection opening, it is necessary to achieve perfect tightness of the control member within the bore of the mixing head by having the control member fit exactly in the bore. This results in an expensive mixing head. This expenditure is also present if a defective mixing head has to be replaced.
Every mixing head is (due to the design of injection jets with the supply lines for the two plastic components) only suitable for processing two plastic masses within narrow limits.
For example, if the mixing ratio of the two plastic components or the amount of the two plastic components per time unit is varied over certain limits, another mixing head is always required. The mixing of the two plastic components is better, when the distance between the jets is smaller. This distance is predetermined by the size of the control member. The distance is particularly large, when the mixing chamber is incorporated into the control member. The diameter of the control member has to be of such a size that the grooves running parallel in one plane to the mixing chamber may be formed in the control member without weakening it.
It is, therefore, an outstanding object of the invention to provide an apparatus for producing a chemical reaction mixture from two plastic components, so that a perfect tightness of the control member is achieved without special expenditure, while at the same time the mixing of the two plastic components is improved.
Another object of this invention is the provision of apparatus for mixing in which control member is designed in such a way that the control member may be replaced without difficulty and without change of the mixing ratio.
With these and other objects in view, as will be apparent to those skilled in the art, the invention resides in the combination of parts set forth in the specification and covered by the claims appended hereto.